Existing light emitting diodes (LED) are obtained by mixing a green phosphorescent substance and a red phosphorescent substance to a blue light emitting diode, or mixing a yellow phosphorescent substance and a blue-green phosphorescent substance to a UV light emitting diode. However, with such a method, it is difficult to control colors, and therefore, color rendering is not favorable. Accordingly, color gamut declines.
In order to overcome such color gamut decline and reduce production costs, methods of obtaining green and red in a manner of filming quantum dots and binding the dots to a blue LED have been recently tried. However, cadmium series quantum dots have safety problems, and other quantum dots have significantly decreased efficiency compared to cadmium series quantum dots. In addition, quantum dots have reduced stability for oxygen and water, and have a disadvantage in that the performance is significantly degraded when aggregated. Furthermore, unit costs of production are high since, when producing quantum dots, maintaining the sizes is difficult.